This invention relates to integrated circuits, and in particular to the control of an interface of an integrated circuit.
More particularly, the invention relates to a programmable logic device, and to a technique for controlling an interface of a programmable logic device.
A programmable logic device is an integrated circuit, which can be customized by a circuit designer to perform different functions. When a programmable logic device is supplied by a manufacturer, it is typically not capable of performing any particular function, but must first be configured. Programmable logic devices generally comprise an array of logic blocks, which can be programmed to perform desired functions, and which can be arbitrarily connected to each other, and to the inputs and outputs of the device.
The data required in order to program the logic blocks, and the interconnect structure which lies between the logic blocks, is typically stored in a separate configuration memory device.
Therefore, when beginning use of the programmable logic device, this configuration data must be retrieved from the configuration memory device into the programmable logic device in order to cause it to perform the intended function. Moreover, when programming the programmable logic device, this configuration data must be stored in the configuration memory device, and then retrieved into the programmable logic device to confirm whether the device then performs the intended function. It is while programming the programmable logic device that this is a particular concern, because the programmer may make frequent changes to the configuration data, and may therefore wish to confirm at regular intervals that the changes still cause the device to perform the intended function.